Merhod for the production of a sealing cover and sealing cover produced by said method

ABSTRACT

The sealing cover ( 1 ) comprises a planar support ( 3 ), on which a number of sealing elements ( 4 ) are arranged, each of which is provided for the sealing of a sample container ( 2 ). The planar support ( 3 ) and the sealing elements ( 4 ) are produced from different materials in the same injection moulding tool ( 21 ) by means of two-component injection moulding. The planar support ( 3 ) is detachably connected to the sealing elements ( 4 ) by means of adhesion. The planar support ( 3 ) and the sealing elements ( 4 ) are preferably made from related plastics.

This invention relates to a method for producing a sealing mat having acarrier sheet on which a plurality of sealing elements are arranged,these elements being provided for sealing at least one test tube.

U.S. Pat. No. 5,282,543 discloses a sealing mat which consists of acarrier sheet on which a plurality of sealing elements is integrallymolded. The carrier and the sealing elements are made of the same ordifferent plastics. Test tubes sealed with this sealing mat are storedin a so-called rack. This makes it possible to seal several test tubes,e.g., 48 or 96 in one operation. This also makes it possible to openthese test tubes comparatively quickly and easily by pulling off thesealing mat.

WO 01/17682 discloses a sealing mat with which the carrier sheet isdetachably joined to the sealing elements. The test tubes which are alsoarranged in a rack are sealed with the sealing mat. The carrier sheetcan be pulled away from the test tubes, with the sealing elementsremaining on the test tubes and sealing them. This carrier is formed bya punched film made of a thermoset plastic. Each sealing element ismechanically attached to the carrier sheet. To this end, each sealingelement has an outer and peripheral groove on an upper edge with thecarrier sheet engaging in this groove. The manufacture of this sealingelement is comparatively complex. First the carrier sheet must bemanufactured and punched. Then the carrier sheet must be inserted intoan injection molding machine and the sealing elements must be integrallymolded on this carrier sheet.

The object of this invention is to create a method with which sealingelements can be manufactured less expensively in large numbers. Thesealing mats produced by this method should be reliable in function andin shipping and should in particular make it possible to pull away thecarrier sheet reliably.

This object is achieved according to Claim 1. In the inventive method,connections that are not mechanical but instead are based on an adhesiveforce are created between the carrier sheet and the sealing elementsduring the injection molding operation. This adhesive bonding strengthcan be established very precisely in a wide range by using plastics forthe sealing elements and the carrier sheet such that both plastics haveadequate wetting. The better the proximity of the molecules of the twobonding partners, the greater is the bonding between the carrier sheetand the sealing elements. The adhesive force between a sealing elementand the carrier sheet can be adjusted accurately to the holding force ofthe sealing elements on the test tubes, so that when the carrier sheetis pulled away, the sealing elements remain securely in the test tubes,sealing them tightly. This avoids individual sealing elements beingpulled out of the test tubes when the carrier sheet is pulled away.

One important advantage of the inventive method is regarded as beingthat the adhesive force between the carrier sheet and the sealingelements can be increased to such an extent that a tight bond is formedand thus an embodiment with non-detachable carrier sheets can beproduced. The same injection molding machine may be used here. Only theplastics to be injected need be changed, but they may also be the same.In this case, one need only inject one plastic, and the sealing matproduced in this way is made in one piece of the same plastic. It isthus very simple to switch between production of sealing mats withdetachable sealing elements and production of sealing mats withnon-detachable sealing elements.

This invention also relates to a sealing mat produced by this method.With this mat, each sealing element has a flat connection at the upperedge on which the sealing elements are detachably joined to the carriersheet by adhesive force. According to a refinement of this invention,this connection is formed by a flange directed radially outward. Theconnection is preferably situated on the top side of this flange.

After pulling off the carrier sheet, the sealing elements may be removedindividually from the test tubes. This may be accomplished by machine,which is particularly simple when the sealing elements have anintegrally molded nose on the bottom on the inside, such that this nosecan be gripped with a suitable instrument.

Other advantageous features are derived from the dependent patentclaims, the following description and the drawing.

An exemplary embodiment of this invention is described in greater detailbelow with reference to the drawing, in which:

FIG. 1 shows schematically a section through a part of the inventivesealing mat,

FIG. 2 shows schematically the carrier sheet being pulled away from asealing element,

FIG. 3 shows schematically a section through a part of the inventivesealing mat,

FIG. 4 shows schematically a section through a part of a rack with thetest tubes sealed and inserted into the rack

FIG. 5 shows schematically a section through a part of a die mold and

FIG. 6 shows a section according to FIG. 5, but after injection of thesealing elements and before injection of the carrier sheet.

The sealing mat 1 shown in FIG. 1 has a carrier sheet 3 which ismanufactured from a flexible plastic and has a thickness A ofapproximately 1 mm or more. According to FIG. 3 a plurality ofsuppository-shaped sealing elements 4 is/are attached to a bottom side 7of the carrier 3. The number of these sealing elements 4 which arearranged in regular rows amounts to 16, 48 or 96, for example.Essentially a greater or lesser number of such sealing elements 4 wouldalso be conceivable here. The sealing mat 1 with the sealing elements 4is used for sealing test tubes 2 which are arranged in a so-called rack18 as indicated in FIG. 4 and have a bottom inside 19, a bottom outside20 and a cylindrical wall 9 with an inside 13. This rack 18 has acorresponding number of continuous openings 26 which usually have asquare cross section and each accommodates a test tube 2. These testtubes 2 may be secured in a known way in the rack 18 in a fillingposition and in a storage position. Likewise these test tubes 2 have acode for identification of samples. Reference is made in this regard toEuropean Patent 0 904 841 A1 (Hoffmann-La Roche AG), which describes adevice for handling such racks and test tubes.

The sealing elements 4 have an approximately U-shaped cross sectionaccording to FIG. 1 and each sealing element has a round cylindricalwall 10 and a bottom 11. Near the bottom 11, a peripheral sealing bulge8 is integrally molded on the outside of the wall 10, forming a seal inthe wall of the test tube 2. On the top side of the bottom 11, there isa nose 31 which protrudes upward and which is provided for allowingmachine removal of the corresponding sealing element 4, as explainedbelow. The sealing bulge 8 which protrudes radially outward isintegrally molded on the upper edge of the sealing container [sic] 4having a ring-shaped top side 14 and a bottom side 16 running parallelto that. When the test tube 2 is sealed, this bottom side 16 sits on anend face 17, also ring-shaped, of the test tube 2.

A corresponding opening 5 is arranged above the opening 27 in thecarrier sheet 3. The ring-shaped flat surface 14 together with acorresponding surface on the bottom side 7 of the carrier sheet 3 formsa connection point 28 which can be released by pulling off the carriersheet 3 as illustrated in FIG. 2. The adhesive force of this connectionpoint 28 is greater than the holding force of the sealing element 4 inthe test tube 2. The carrier sheet 3 may thus be pulled away in thedirection of the arrow 12 according to FIG. 2 without removing thesealing element 4 from the test tube 2. After pulling away the carriersheet 3, the sealing elements 4 thus remain tightly on the correspondingtest tubes 2. The connection points 28 are formed by injection moldingof the carrier sheet 3 on the sealing elements 4, as is also apparentfrom the method described below.

To produce the sealing mat 1, the injection die mold 21, which is merelyindicated in FIG. 5 and FIG. 6, is used. It has two mold parts 22 and 23and two essentially known injection molding units (not shown here). Themold part 23 has shoulders 30, each forming an intermediate space 24with the mold part 22 in which a sealing element is injected. Theplastic used for injecting the sealing elements is preferablypolypropylene, polyethylene or an ethylene-vinyl acetate copolymer(EVA).

After injection of the sealing elements 4, the mold part 23 is raisedfrom the mold part 22 in such a way that an interspace 25 of thethickness A is formed. Plastic is injected into this interspace 25 usinga second injection molding apparatus (not shown here). This plastic is athermoplastic elastomer, e.g., SEBS or SBS or a silicone rubber. As FIG.6 shows, the areas 14 of the flange 8 are facing this interspace 25. Oninjection of plastic into the interspace 25, this plastic is thusintegrally molded onto the flange 8 in the area of the surfaces 14. Ifthe two plastics that are injected with the injection molding units havegood wettability, the connection 28 mentioned above is formed on thesurfaces 14, its adhesive force depending on the wetting of the selectedplastics and the proximity of the molecules of the two partners in thebonding. If the wetting and the proximity of the molecules between thesetwo plastics are great, then this adhesive force will be greataccordingly. In the limiting case in which the two plastics are thesame, the carrier sheet will be integrally molded onto the sealingelements 4 and in this case the carrier sheet 3 will no longer bedetachable from the sealing elements 4. If the wetting and proximity ofthe molecules of the two plastics are comparatively great, then theadhesive force of the connection 28 will be lower accordingly. Throughappropriate choice of the two plastics, thus essentially any desiredadhesive force can be achieved. In practice, this adhesive force isselected so that the sealing elements 4 adhere reliably to the carriersheet 1 for application to the test tubes 2 but at the same time thecarrier sheet 3 can be pulled away, as explained above. In a preferredexemplary embodiment, the carrier sheet 3 is made of SEBS or SBS and thesealing elements 4 are made of EVA. However, other combinations ofplastics are also conceivable, but it is essential that both the carriersheet 3 and the sealing elements 4 are made of a rubber elastic plastic.Through a suitable choice of the two plastics, it is thus possible toproduce optionally a sealing mat 1 with a removable carrier sheet 3 or asealing mat in which the sealing elements 4 are fixedly attached to thecarrier sheet 3.

If the sealing elements 4 are detachably joined to the carrier sheet 3,then the carrier sheet 3 can be pulled away from the sealing elements 4,as explained above. The test tubes are thus individually tightly sealedwith one sealing element 4 each. In the suitable storage position, thesetest tubes 2 can thus be stored and opened individually as needed. To doso, the sealing elements 4 are each gripped on the nose 26 [sic] using atool (not shown here) and pulled upward out of the corresponding testtube 2. The holding force of the sealing elements 4 in the test tubes 2,in particular due to the adhesion to the inside 13, is selected in eachcase so that it is smaller than the holding force of the test tubes 2 inthe rack 18. When the sealing elements 4 are pulled out of the testtubes 2, they thus remain in the rack 18. The adhesive force of theconnection 28, the holding force of the sealing elements 4 and theholding force of the test tubes 2 in the rack 18 are thus coordinated.The adhesive force 28 may be adjusted essentially continuously andprecisely through the choice of the plastics, as explained above.

1. Method of producing a sealing mat (1) having a carrier sheet (3) onwhich are arranged multiple sealing elements (4), each being providedfor sealing a test tube (2), characterized in that the carrier sheet (3)and the sealing elements (4) are made of different materials in the sameinjection die mold (21) by two-component injection molding, and thecarrier sheet (3) is thus detachably joined to the sealing elements (4)by adhesion.
 2. Method as claimed in claim 1, characterized in that thecarrier sheet (3) and the sealing elements (4) are made of relatedplastics.
 3. Method as claimed in claim 1 or 2, characterized in thateach sealing element has a flange (8) projecting outward on an upperedge, the carrier sheet (3) being integrally molded onto this flange. 4.Method as claimed in claim 3, characterized in that the flange (8) hasan upper surface (14) onto which the carrier sheet (3) is integrallymolded.
 5. Method as claimed in any one of claims 1 through 4,characterized in that the carrier sheet (3) is made of a thermoplasticelastomer.
 6. Method as claimed in any one of claims 1 through 4,characterized in that the carrier sheet (3) is made of silicone rubber.7. Method as claimed in any one of claims 1 through 4, characterized inthat the carrier sheet (3) is made of SEBS or SBS.
 8. Method as claimedin any one of claims 1 through 4, characterized in that the sealingelements (4) are made of polypropylene or polyethylene.
 9. Method asclaimed in any one of claims 1 through 7, characterized in that thesealing elements (4) are made of EVA.
 10. Method as claimed in any oneof claims 1 through 9, characterized in that the bonding strengthbetween the carrier sheet (3) and one of the sealing elements (4) isessentially greater than the holding force of a sealing element (4) in atest tube (2).
 11. Method as claimed in any one of claims 1 through 10,characterized in that first the sealing elements (4) are injected andthen the carrier sheet (3) is injected.
 12. Sealing mat produced by themethod as claimed in claim 1, characterized in that each sealing element(4) has a flat connection (28) on the upper edge, where the sealing (4)is detachably joined to the carrier sheet (3) by adhesion.
 13. Sealingmat as claimed in claim 12, characterized in that the flat connection(28) is arranged on an upper edge of the sealing element (4). 14.Sealing mat as claimed in claim 13, characterized in that the sealingelement (4) has a flange (8) protruding outward on said upper edge andthe flat connection (28) is formed by an end face (14) of this flange(8).
 15. Sealing mat as claimed in any one of claims 12 through 14,characterized in that the sealing elements (4) are made of polypropyleneor polyethylene and the carrier sheet (3) is made of a thermoplasticelastomer.
 16. Sealing mat as claimed in any one of claims 12 through15, characterized in that the carrier sheet (3) and the sealing elements(4) are made of different but related plastics.
 17. Sealing mat asclaimed in any one of claims 12 through 16, characterized in that thecarrier sheet (3) is made of SEBS or SBS and the sealing elements aremade of EVA.
 18. Sealing mat as claimed in any one of claims 12 through17, characterized in that each sealing element (4) has a nose (31) onthe top side of a bottom (11) on which the sealing element (4) can begripped and pulled away from the test tube (2).